[petsc-dev] MATOP_MAT_MULT

[Zhang, Hong]

Pierre,
The old API, MatMatMult(), MatPtAP() ... are still available as wrappers to the new API:
MatProductCreate()
MatProductSetType(,MATPRODUCT_AB/PtAP)
MatProductSetFromOptions()
MatProductSymbolic()
MatProductNumeric()
You do not need to change your code. When you call MatMatMult() with seqsbaij and dense matrices, a detailed error message will be out from MatProductSetFromOptions() (or MatMatMult() if you use the wrapper).

I'll discuss Jose's usage in next email.
Hong
________________________________
From: Pierre Jolivet <pierre.jolivet at enseeiht.fr>
Sent: Tuesday, April 21, 2020 10:53 AM
To: Zhang, Hong <hzhang at mcs.anl.gov>
Cc: petsc-dev <petsc-dev at mcs.anl.gov>
Subject: Re: [petsc-dev] MATOP_MAT_MULT



On 21 Apr 2020, at 5:22 PM, Zhang, Hong <hzhang at mcs.anl.gov<mailto:hzhang at mcs.anl.gov>> wrote:

Pierre,
MatMatMult_xxx() is removed from MatOps table.

Shouldn’t there be a deprecation notice somewhere?
There is nothing about MATOP_MAT_MULT in the 3.13 changelog https://www.mcs.anl.gov/petsc/documentation/changes/313.html
For example, I see that in SLEPc, José is currently making these checks, which are in practice useless as they always return PETSC_FALSE? https://gitlab.com/slepc/slepc/-/blob/master/src/sys/classes/bv/impls/contiguous/contig.c#L191
(Maybe José is aware of this and this is just for testing)

MatMatMult() is replaced by
MatProductCreate()
MatProductSetType(,MATPRODUCT_AB)
MatProductSetFromOptions()
MatProductSymbolic()
MatProductNumeric()

Where/when do you need query a single matrix for its product operation?

I didn’t want to bother at first with the new API, because I’m only interested in C = A*B with C and B being dense.
Of course, I can update my code, but if I understand Stefano’s issue correctly, and let’s say my A is of type SBAIJ, for which there is no MatMatMult, the code will now error out in the MatProduct?
There is no fallback mechanism? Meaning I could in fact _not_ use the new API and will just have to loop on all columns of B, even for AIJ matrices.

Thanks,
Pierre

Hong

________________________________
From: petsc-dev <petsc-dev-bounces at mcs.anl.gov<mailto:petsc-dev-bounces at mcs.anl.gov>> on behalf of Pierre Jolivet <pierre.jolivet at enseeiht.fr<mailto:pierre.jolivet at enseeiht.fr>>
Sent: Tuesday, April 21, 2020 7:50 AM
To: petsc-dev <petsc-dev at mcs.anl.gov<mailto:petsc-dev at mcs.anl.gov>>
Subject: [petsc-dev] MATOP_MAT_MULT

Hello,
Am I seeing this correctly?
#include <petsc.h>

int main(int argc,char **args)
{
  Mat               A;
  PetscBool         hasMatMult;
  PetscErrorCode    ierr;

  ierr = PetscInitialize(&argc,&args,NULL,NULL);if (ierr) return ierr;
  ierr = MatCreate(PETSC_COMM_WORLD,&A);CHKERRQ(ierr);
  ierr = MatSetType(A,MATMPIAIJ);CHKERRQ(ierr);
  ierr = MatHasOperation(A,MATOP_MAT_MULT,&hasMatMult);CHKERRQ(ierr);
  printf("%s\n", PetscBools[hasMatMult]);
  ierr = PetscFinalize();
  return ierr;
}

=> FALSE

I believe this is a regression (or at least an undocumented change) introduced here: https://gitlab.com/petsc/petsc/-/merge_requests/2524/
I also believe Stefano raised a similar point there: https://gitlab.com/petsc/petsc/-/issues/608
This is a performance killer in my case because I was previously using this check to know whether I could use MatMatMult or had to loop on all columns and call MatMult on all of them.
There is also a bunch of (previously functioning but now) broken code, e.g., https://www.mcs.anl.gov/petsc/petsc-current/src/mat/impls/transpose/transm.c.html#line105 or https://www.mcs.anl.gov/petsc/petsc-current/src/mat/impls/nest/matnest.c.html#line2105
Is this being addressed/documented?

Thanks,
Pierre

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